Window Blind Solar Energy Management System

ABSTRACT

Disclosed is a window blind solar energy management system for capturing solar energy to manage illumination and temperature within a defined space. Blinds comprising curved louvers are hung from the internal frame of a window, each louver having a concave, highly reflecting specular mirrored surface that focuses incoming solar beam radiation onto a thin area on the back of the adjacent louver. The angle of the louvers is adjusted by an integral automatic controller so that the thin strip of light can be focused on one or two of three regions on the back of the adjacent louver which are designed to either reflect, absorb, or reject the incoming light.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims benefit of copending U.S.Provisional Patent Application Ser. No. 61/615,389 entitled “WindowBlind Solar Energy Management System,” filed with the U.S. Patent andTrademark Office on Mar. 26, 2012 by the inventor herein, and copendingU.S. Provisional Patent Application Ser. No. 61/703,606 entitled “WindowBlind Solar Energy Management System,” filed with the U.S. Patent andTrademark Office on Sep. 20, 2012, the specifications of which areincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to radiant energy management, and moreparticularly to systems for capturing solar energy to manageillumination and temperature within a defined space.

BACKGROUND OF THE INVENTION

As an architectural feature, a window provides daylight to an interiorspace and allows the building occupants a view to the outside. Whendirect beam solar radiation falls directly on a window, the light thatenters has an intensity of several hundred watts per square meter and isgenerally too bright to be used directly as illumination. The light mustbe attenuated, diffused, or reflected onto the ceiling and walls of theroom by a window treatment to provide comfortable illumination. Daylightharvesting systems are now commonly employed which automatically dim orturn off lighting in the vicinity of windows when natural light isavailable to reduce energy consumption and building heat load.

Typical solutions for attenuation of incoming sunlight include opaque ortranslucent shades, blinds, and curtains. These can reflect a portion ofthe incoming solar radiation to reduce light levels and glare, but havethe disadvantage of having only coarse controllability and do notprovide illumination to the area away from the window deeper into theroom. More sophisticated blinds and fixed reflecting louvers areavailable that can reflect light up towards the ceiling to bring lightfurther into the room, but the degree of illumination is not directlycontrollable.

Another common solution to handling the solar energy on a verticalwindow is coatings and films that change the optical properties of thewindow glazing to either reflect or absorb selective bands of thevisible and infrared spectrum. These have the advantage of reducing theneed for internal window treatments, but these are typically permanentchanges to the window characteristics and so they permanently reduce theamount of solar energy available for useful illumination and heating.There is considerable research and development in windows withelectrochromic coatings that allow direct control of the transmissivityof the glazing. These currently suffer from high cost and slow reactiontime.

There is believed to be a window treatment commercially available inEurope that allows the user to selectively prefer heating or lighting,but the product does not provide for complete reflection of a portion ofunwanted solar energy.

Moreover, the solar radiation into the side windows of a building ispresent for only a few hours of the day—either morning, noon, orafternoon. To take best advantage of this intermittent heat source, itis common practice in passive solar heating design to include some typeof thermal storage so that the heat gathered over, for example, three orfour hours can be spread over a longer period to avoid overheatingduring the sun periods and to provide comfort for hours afterwards.

Typical window shades block or absorb sunlight and convert the sunlightinto heat on the shades which is brought into the room by thermalconvection. The temperature of the air that rises from the back of thewindow shade is typically only 10° or 15° warmer than the room air. Thisprovides little temperature differential to drive thermal storage. Avery large mass is required to store a significant amount of heat withsuch a small temperature difference. Therefore, typical window shadesand blinds have very little ability to store any of the heat andtherefore the heat that they do provide to the room is highly variablein a function solely of the heat input through the window.

Therefore, there remains a need in the art of solar energy managementsystems to simultaneously provide for the control of lighting andtemperature in a room that is easy to manufacture and deploy and thatreliably manages both lighting and temperature conditions over anextended period and in varied conditions (such as varying sunlightconditions).

SUMMARY OF THE INVENTION

Disclosed is a system and method for harvesting solar energy, and moreparticularly an automated, tracking internal Venetian window blind thatprovides even, precisely controlled illumination of the room whilesimultaneously providing either radiant heat when the building is inheating mode or heat rejection when the building is in cooling mode.

The invention employs curved louvers similar in appearance to Venetianblinds. The blinds are hung from the internal frame of the window, whichis preferably clear glass with no reflecting or other energy managementfeatures. Each louver has a highly reflecting specular mirrored surfaceon the front of the louver (the side facing outside). The louver has theconcave side up (opposite of conventional blinds). The shape of thelouver is designed to focus the incoming solar beam radiation onto athin area on the back of the adjacent louver.

The angle of the mirrored louvers is adjusted by an integral automaticcontroller so that the thin strip of light reflected from the front ofone louver can be focused on one or two of three regions on the back ofthe adjacent louver. The three areas of the louver are designed toeither reflect, absorb, or reject the incoming light; the controller maydetermine the desired louver angle based on inputs from local sensors,the building energy management system, and user preferences. The threeareas are designed so that the solar energy usage can be smoothlyadjusted from, at one extreme, full heating, then to a mix of heatingand lighting, then to full lighting, then to a mix of lighting andcooling, and then to full cooling (rejection). This allows the priorityuse of the sunlight to be lighting. Then the excess energy can be eitherconverted to radiant heat or sent back outside.

The system described herein is thus configured to control both lightingand heating load on a building. With regard to lighting, the mostbeneficial use of incoming solar energy is in the form of daylightingfor illumination of the room. Natural light has many advantages overartificial lighting, including improved visual acuity, health andproductivity benefits, and lower heat gain per unit of light deliveredthan typical electric lighting. A typical fluorescent light fixtureprovides about 70 lumens of light per watt of power input, compared tonatural daylight at 100 lumens per watt. So for the same degree ofillumination, daylighting requires zero electric light powerconsumption, and also has 30% lower thermal load on the air conditioningsystem compared to typical artificial light. The high value of thelighting functionality is the reason that the system described herein isdesigned to have light diffusion and delivery as the primary orpreferred mode, with heating/cooling as secondary. As noted above,illumination coming directly from a window must be attenuated to a largedegree to avoid uncomfortable glare. This attenuation, while improvingthe lighting aspects, is undesirable to the extent that it increasesheat generation and makes use of only a portion of the incoming light asillumination. A much larger portion of the incoming light can be usedfor illumination if the light is reflected up onto the ceiling deeperinto the room; this is what the system described herein accomplishes.When the blind is in lighting mode, some or all of the concentratedlight is focused onto a secondary mirror which both reflects andscatters the light up towards the ceiling, away from the occupant's eyelevel to provide even, reflected light to the space from above. Theamount of illumination provided can be precisely controlled by directinga portion of the concentrated beam onto either the heating or coolingregions of the receiver. Illumination is only useful and desired whenthe room is occupied; thus, the illumination from the proposed productcan be directly controlled by manual switching or an occupancy sensor toswitch to heating or cooling mode as desired.

Most of the functionality of the proposed product is directed towardsmanaging direct incoming solar radiation. When the amount of direct beamsolar radiation is low due to cloud cover or the position of the sun inthe sky, the blinds can be programmed to move to an open position oreven to a fully raised position to allow maximum diffuse radiation intothe space and to provide the maximum view to the outside for theoccupant.

With regard to the heating load on a building, such heating load isdependent primarily on the outside air temperature, the degree ofthermal insulation of the building, the amount of internal heatgeneration in the building, and the amount of incoming solar radiationthrough windows and skylights. Given the combination of these factors,each building has a “balance point” temperature where internal heatgains equal the heat loss to the outside. When the outside airtemperature falls below this balance point, heating is required tomaintain comfortable internal temperature, and above this point, coolingis required. Commercial buildings typically have tighter envelopes andhigher internal heat generation intensities, and have lower balancepoint temperatures than residential buildings. If the energytransmitting properties of the window area can be directly controlled,this balance point can be extended to a “balance band” where neitherheating nor cooling is required to maintain internal comfort levels.Thus, controlling the properties of the windows in buildings with highlevels of fenestration has the potential to save a great deal of energyin the heating and cooling systems, and can be a key element to a NetZero building.

The objective of the heating function of the system described herein isto convert the incoming solar beam radiation into radiant thermal energythat can be projected deep into the room to enhance the thermal comfortof the occupants. The thermal comfort of a building occupant is afunction of the temperature and velocity of the immediately surroundingair as well as the temperature and radiant properties of the internalsurfaces of the room. If a person is sitting near a large window whichhas a low temperature of the glass surface, he may feel cold even thoughthe air temperature near his skin is warm. This is because his body willbe radiating heat to the window because the window surface temperatureis colder than his skin temperature. Conversely, it is possible for oneto feel comfortable in a room with relatively low air temperature if thetemperature of the walls and floor are relatively high. This is theprinciple behind radiant floor heating in homes and commercial buildingswhereby energy savings can be achieved by lower indoor air temperatureswhile maintaining or improving comfort.

In terms of the system described herein, the primary desiredcharacteristic for heating is to absorb the incoming solar radiation toheat the room. Secondarily, it is desirable to have a significantfraction of the heat be radiated into the room as opposed to convectedas hot air. Heat that is radiated from the window blind counters the“cold window” effect and can instantaneously project the heat to theoccupant and the surfaces in the room, as opposed to heating the airalone and relying on ventilation to move the heat into the room. Thedegree of radiation from a surface is proportional to the emissivity ofthe surface and to the fourth power of absolute temperature. A surfacewith a high emissivity that is heated to 170 F will project about 40% ofits heat as radiation into the room, with the balance transferred asheat to the room air by convection. It is thus desired that the thermalreceiving area of the blind reach a high temperature by having highabsorptivity and emissivity, combined with a low surface area andthermal isolation from conductive losses.

In order to maximize the usage of the captured heat, and in accordancewith certain aspects of an embodiment of the invention, a room ceilingmay also be configured as a thermal storage medium capable of storingheat radiated from the window over an extended duration.

Likewise, when the building energy balance is positive, the HVAC systementers cooling mode. In most residential buildings and many commercialbuildings, one of the most significant components of building heat loadis the solar heat gain through the windows. When in cooling mode, themost desirable characteristic of the window, after providing the desiredillumination, is to reflect the solar radiation back to the outsideenvironment. The system described herein accomplishes this by directingthe focused beam of concentrated light onto a secondary mirror that isoriented to reflect the radiation straight out of the window. As withthe heating mode, the blind controller can proportionally allocate theamount of energy directed to illumination versus rejection. This allowslighting to be the primary mode and heat rejection secondary.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the present invention may be betterunderstood by those skilled in the art by reference to the accompanyingdrawings in which:

FIG. 1( a) is a front perspective view of a window blind solar energymanagement system according to certain aspects of an embodiment of theinvention.

FIG. 1( b) is rear perspective view of the window blind solar energymanagement system of FIG. 1( a).

FIG. 2 is a cross-sectional view of a single louver for use in thesystem of FIGS. 1( a) and 1(b).

FIG. 3 is a close-up, bottom perspective view of the single louver ofFIG. 2.

FIGS. 4( a)-4(c) are schematic views of energy flows using the system ofFIGS. 1( a) and 1(b) and louvers as shown in FIGS. 2 and 3 in each of aheating mode, a lighting mode, and a cooling mode for low sun angles.

FIGS. 5( a)-5(c) are schematic views of energy flows using the system ofFIGS. 1( a) and 1(b) and louvers as shown in FIGS. 2 and 3 in each of aheating mode, a lighting mode, and a cooling mode for high sun angles.

FIG. 6 is a close-up, bottom perspective view of a single louver for usein the system of FIGS. 1( a) and 1(b) according to further aspects of anembodiment of the invention.

FIGS. 7( a)-7(c) are schematic views of energy flows using the system ofFIGS. 1( a) and 1(b) and louvers as shown in FIG. 6 in each of a heatingmode, a lighting mode, and a cooling mode for midrange sun angles.

FIG. 8 is a schematic view of a room in which the system of FIGS. 1( a)and 1(b) is in use.

FIG. 9 is a graph showing blind energy division versus louver angle forthe system of FIGS. 1( a) and 1(b).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of a particular embodiment of theinvention, set out to enable one to practice an implementation of theinvention, and is not intended to limit the preferred embodiment, but toserve as a particular example thereof. Those skilled in the art shouldappreciate that they may readily use the conception and specificembodiments disclosed as a basis for modifying or designing othermethods and systems for carrying out the same purposes of the presentinvention. Those skilled in the art should also realize that suchequivalent assemblies do not depart from the spirit and scope of theinvention in its broadest form.

FIGS. 1( a) and 1(b) provide front and rear perspective views,respectively, of a window blind solar energy management system (showngenerally at 100) according to certain aspects of an embodiment of theinvention. As shown in FIGS. 1( a) and 1(b), the system has thesuperficial appearance of a typical Venetian blind having multiplelouvers 110. The enclosure 120 at the top of the system is configured tomount to a window frame (not shown), and houses the motorized mechanismsthat raise and lower the blind and adjust the angle of the louvers.While not shown on the figures, those of ordinary skill in the art willrecognize that such motorized mechanisms are well known in the art andare thus not discussed further here. Also in the enclosure 120 are thecontroller board and the sensors (not shown). Sensors may include roomtemperature sensors, occupancy sensors, and an incoming solar radiationsensor. Optionally, one solar radiation sensor can provide solar datafor all the blinds on one side of a building.

FIG. 2 shows a cross-sectional view of a single louver 110 of FIG. 1 inaccordance with certain aspects of a particularly preferred embodimentof the invention. The louver 110 is composed of two components: themirror 112 and a solar energy redirection assembly, which in accordancewith certain aspects of an embodiment of the invention comprisesreflected light and thermal receiver assembly 114. The mirror 112 ismade of a single strip of preferably anodized aluminum sheet that has ahighly reflective coating on one side. The shape of the curve of mirror112 is designed to enable the incoming light to be focused on a narrowstrip on the back of the adjacent louver. The range of possible anglesof the incident sunlight ranges from zero (horizontal as at sunrise andsunset) and 90 degrees (sun at zenith point). The constraints on theoptics design of mirror 112 are such that the degree of focus cannot beperfect over the whole range of possible sun angles. However, the shapeof mirror 112 can be optimized to have the best focusing efficiency atthe sun angles that have the most solar energy over the year, dependingon the location of the building and the orientation of the window. It isanticipated that an average concentration ratio of about 10 isachievable. The shape of mirror 112 can either be a faceted or smoothcurve. The faceted shape is more straightforward to manufacture, as aseries of simple bending operations can produce the desired shape. It ispossible to design the shape such that each bend has the same angle,while the distance between angles varies. Keeping the angle constantsimplifies and speeds the bending operation, because the material can beindexed over repeated identical bends. The continuously curved shape ispotentially more aesthetically pleasing but requires more expensivetooling to achieve.

The region of the louver that is closest to the window is designated asthe reflected light and thermal receiver assembly 114, where thefeatures are located that convert the concentrated light beam to itsuseful purposes. With particular reference to the cross-sectional viewof FIG. 2 and the bottom perspective view of FIG. 3, and in accordancewith certain aspects of the embodiment shown in those Figures, a thermalreceiver 116 is positioned at the upper end of the receiver assembly114. This thin strip, preferably about 1 cm in width, is preferablyattached using adhesive materials 118 that have very low thermalconductivity. This allows the heating strip of thermal receiver 116 toachieve high temperature to accomplish the desired radiation asmentioned above. The sun-facing surface of the thermal receiver 116 hashigh absorptivity (e.g., >0.9), and low emissivity (e.g., <0.1). Thisallows the surface to absorb solar radiation and to avoid reradiatingthe heat right back out the window. The back side 117 of the surface(not facing the sun) is painted with high emissivity coating that allowsthe back side 117 of the surface to reflect radiated energy off the backof the louver and towards the ceiling and into the room. If thetemperature of the thermal receiver 116 is to be high enough to be aburn hazard, the blind can be outfitted with features that prevent ahand from reaching into the space between the louvers 110, such as wiresor fibers strung on the room side of the blind. These might makecleaning of the blinds difficult, so a preferred solution would bewarning labels.

Below the thermal receiver 116 is an aperture 120 that is cut orotherwise formed in the mirror 112 to allow light to strike a secondarymirror 122 that provides illumination. The shape and surface propertiesof secondary mirror 122 are selected to direct the light away from theoccupant's direct field of view, towards the ceiling of the room. Thisdegree of direction and diffusion of the light is accomplished bycontrolling the radius of a concave smooth or faceted shape of mirror112 which takes the focusing beam and reflects the desired beam width upto the ceiling of the room. To avoid distracting images of the reflectedlight on the ceiling, the surface of the reflector 122 is preferablymade of partially specular, partially diffuse material. These materialsare known to those of ordinary skill in the art, as they are commonlyused in the design of lighting fixtures to direct light from bulbs whileavoiding imaging and glare. The advantage of re-diffusing a highlyconcentrated beam is that the reflecting and diffusing can beaccomplished with a very small amount of material, about one centimeterwide.

In addition to the focused and re-reflected direct beam radiation, afraction of the diffuse sky radiation is also reflected by the louvers110 into the space. Roughly speaking, the diffuse radiation (reflectedfrom clouds or scattered by the sky) that comes from the part of the skybetween the sun and the horizon will be reflected into the room. If theoccupant is close to the window, it is possible that the light projectedfrom the lower louvers 110 may cause uncomfortable glare. If this is aproblem, an alternative option is to create horizontal zones or regionsof the blind, where the heat rejection/heating is performed by the lowerregions and the daylighting is provided by the upper regions. If thelouver angle of each zone is independently controllable, this wouldallow maximum flexibility and control for each zone to be in each mode.Alternatively, each zone could have a fixed offset angle from theadjacent zone such that the heat/light/cooling mode of each zone wouldbe a nonuniform function of the single louver angle setting.

As the beam is directed further downwards by the controller, the lightthen passes through the slits that are cut in each louver (to formaperture 120) and more fully hits the secondary mirror 122. The raysthat strike the lower portion of the secondary mirror 122 are at anangle closer to the horizontal than the rays that strike the upperportion. The mirror shape is designed to focus the converging rays intoa beam that is projected onto the ceiling (including by furtherreflecting such light off of louvers 110, as best shown in FIGS. 4 and5). The front reflecting surface of the adjacent mirror 112 serves toprevent any of the reflected light from leaving the blind at a shallowangle, preventing any possibility of glare to the room occupant.

For cooling (heat rejection), as the mirrors 112 are further rotatedcounter-clockwise in the figure, the light beam is directed away fromthe lighting aperture 120 and towards the other secondary mirror 124which reflects the rays, causing them to go directly out of the window,which will result in less re-reflection of the light and a greaterportion being rejected from the building envelope. Further positioningof the louvers 110 beyond the setting shown results in 100% of the heatbeing rejected, which would be the desired setting when the room isunoccupied in cooling mode.

FIGS. 4 and 5 show the function of each of the energy managing surfaceson louvers 110 and the resulting energy flows for varying sun and louverangles. Specifically, FIG. 4( a) shows louvers 110 oriented in a heatingmode when sunlight 400 enters the window 300 at a low sun angle.Incoming light 400 is reflected off of a first mirror 112 and isdirected into a narrow beam that impacts thermal receiver 116 on theadjacent louver, the back side of which in turn transmits radiatedenergy 402 towards the ceiling and into the room. FIG. 4( b) showslouvers 110 oriented in a lighting mode when sunlight 400 enters window300 at a low sun angle. Incoming light is again reflected off of a firstmirror 112 and is directed into a narrow beam that impacts secondarylighting mirror 122 on the adjacent louver, which reflects light 404towards the ceiling and into the room. Likewise, FIG. 4( c) showslouvers 110 oriented in a cooling mode when sunlight 400 enters window300 at a low sun angle. Here, incoming light is once again reflected offof a first mirror 112 and is directed into a narrow beam that impactssecondary cooling mirror 124 on the adjacent louver, which reflectslight 406 back out through window 300 and away from the room.

Similarly, FIG. 5( a) shows louvers 110 oriented in a heating mode whensunlight 400 enters the window 300 at a high sun angle. Incoming light400 is reflected off of a first mirror 112 and is directed into a narrowbeam that impacts thermal receiver 116 on the adjacent louver, the backside of which in turn transmits radiated energy 502 towards the ceilingand into the room. FIG. 5( b) shows louvers 110 oriented in a lightingmode when sunlight 400 enters window 300 at a high sun angle. Incominglight is again reflected off of a first mirror 112 and is directed intoa narrow beam that impacts secondary lighting mirror 122 on the adjacentlouver, which reflects light 504 towards the ceiling and into the room.Likewise, FIG. 5( c) shows louvers 110 oriented in a cooling mode whensunlight 400 enters window 300 at a high sun angle. Here, incoming lightis once again reflected off of a first mirror 112 and is directed into anarrow beam that impacts secondary cooling mirror 124 on the adjacentlouver, which reflects light 506 back out through window 300 and awayfrom the room.

With regard to further aspects of an embodiment of the invention, thesurfaces on louvers 110 that provide heating and cooling functions mayalternatively be reversed, which in certain implementations may providebetter performance and which will be easier to manufacture. Moreparticularly, and as shown in the bottom perspective view of FIG. 6,cooling secondary mirror 124 may be positioned at the upper end ofreflected light and thermal receiver assembly 114. This configurationavoids the potential challenges relating to attachment of thermalreceiver 118 directly to primary mirror 112, as temperature variationsin thermal receiver 118, in turn causing thermal expansion with everyheating cycle, could make such attachment difficult to maintain. Thecooling secondary mirror 124 reflects almost all of its light andtherefore is not expected to have significant temperature variations.

With regard to the embodiment shown in FIG. 6, the aperture 120 forallowing the light beam to strike lighting secondary mirror 122 is againformed by a series of slots cut at the base of the primary mirror 112.However, in this configuration, the slots perform two functions. Inaddition to allowing light to pass through to strike lighting secondarymirror 122, the narrow strips of material that create aperture 120 alsoserve to thermally isolate thermal absorber 116 from primary mirror 112.Load calculations show that with 90% of the material cutaway and 10% ofthe mirror left as the bridge, a large temperature difference betweenthermal absorber 116 and primary mirror 112 can be maintained.

In this embodiment, thermal radiator 117 is positioned adjacent aperture120 (opposite cooling secondary mirror 124), where it has a better viewof the ceiling of the room. The heat radiated from the top of thethermal radiator 117 is reflected by secondary lighting mirror 122, thefront face of primary mirror 112, and the back face of the adjacentprimary mirror. These surfaces are all highly reflective to infraredradiation and serve to direct such radiation towards the ceiling of theroom where, with regard to further aspects of an embodiment of theinvention, it can be captured by thermal storage media as discussed ingreater detail below. In this embodiment, all of the high temperaturesurfaces (the thermal absorber 116, lighting secondary mirror 122, andthermal radiator 117) are pointing away from the occupants of the room.This significantly reduces the burn hazard associated with hightemperature components. As shown in FIG. 6, these high temperaturesurfaces would be difficult to touch if one were casually placing one'sfingers near the louvers 110. This effectively increases the upper limitof the safe temperature of the thermal receiver 116. It is alsobeneficial in that the fraction of the heat that is lost by conductionoccurs on the window side of the blind as opposed to the room side ofthe blind. Having the heat released on the window side of the blindcounteracts the downward draft of cold air that comes from a cold windowsurface.

The path of the energy flows using a louver as shown in FIG. 6 are shownin the diagrams of FIGS. 7( a)-7(c) for a midrange sun angle.Specifically, FIG. 7( a) shows louvers 110 oriented in a heating modewhen sunlight 400 enters the window 300 at a midrange sun angle.Incoming light 400 is reflected off of a first mirror 112 and isdirected into a narrow beam that impacts thermal receiver 116 on theadjacent louver, the back side of which in turn transmits radiatedenergy 702 towards the ceiling and into the room. FIG. 7( b) showslouvers 110 oriented in a lighting mode when sunlight 400 enters window300 at a midrange sun angle. Incoming light is again reflected off of afirst mirror 112 and is directed into a narrow beam that impactssecondary lighting mirror 122 on the adjacent louver, which reflectslight 704 towards the ceiling and into the room. Likewise, FIG. 7( c)shows louvers 110 oriented in a cooling mode when sunlight 400 enterswindow 300 at a midrange sun angle. Here, incoming light is once againreflected off of a first mirror 112 and is directed into a narrow beamthat impacts secondary cooling mirror 124 on the adjacent louver, whichreflects light 706 back out through window 300 and away from the room.

While FIGS. 7( a)-7(c) show the louvers of FIG. 6 only at use in amidrange sun angle setting, such louvers, as well as those shown inFIGS. 2 and 3, can all be used throughout the sun angles that mightimpact the system of FIGS. 1( a) and 1(b) to manage lighting andtemperature within the room in which such system is installed.

Also provided is a low cost smart controller board that manages theheight of the blinds and the angle of the louvers. The key controlinputs are:

total solar radiation incident on the window;

fraction of solar radiation that is direct vs. diffuse;

mode of the building heating/cooling system;

desired room illumination level; and

actual room illumination level.

With regard to another aspect of an embodiment of the invention, thewindow blind system described above may concentrate the sun's rays by afactor of ten onto thermal absorbing strip 116. This thin strip isdesigned to radiate most of the incoming solar energy towards theceiling at a much higher temperature than the air convected from atypical blind or shade. Depending on the angle of the sun, this thinstrip will reach temperatures of 150 to 180° F. This provides a muchhigher temperature differential to drive thermal storage.

With reference to the schematic view of FIG. 8, projecting the heat awayfrom the window 300 and towards the ceiling 800 allows the ceilingitself to become the thermal storage medium. Heat radiated from theceiling 800 has a much better view factor to the occupants of the roomand can provide a more comfortable radiant environment than heatradiated from the window. The ceiling tiles in a typical suspendedceiling design are capable of carrying a significant amount of weightfor thermal storage media. Thermal storage in the ceiling tiles can beaccomplished in a number of ways. For existing ceiling tiles, the tilescan be painted with paints that are impregnated with microencapsulatedphase change materials. The phase change materials inside the microencapsulation can be designed to change phase at a temperature that istuned to what the inventive blinds described herein can deliver.Similarly, the phase change material can be embedded in the ceilingtiles themselves; that is, the microencapsulated phase change pelletscan be mixed with the media of which the ceiling tiles are made.Finally, bags containing the phase change material can simply be placedon top of the ceiling tiles; however, the insulating property of theceiling tiles can isolate the phase change material from the heatsource. In this case, the performance could be improved if the ceilingtiles were made of a more conducting material such as paintedsheet-metal. In any case, the ceiling tiles should be made of materialswhich are highly reflective of visible light and also provide somediffusion in the reflection properties.

An exemplary system design utilizing this thermal storage configurationis as follows. A multistory office building with an exposed east orsoutheast facing side that has clear glass windows installed on thatside could have the entire side of the building act as a solar thermalcollector with the heat that is collected being delivered as comfortableradiant heat from the ceiling spread out from the mornings through themidafternoon. For south facing glass, the majority of the direct solarradiation would occur in the late morning and early afternoon in thewinter when the heat is most needed. The thermal storage would spreadthe heat over several hours through the late afternoon. The thermalstorage would be less useful for west facing windows because theavailable heat would be spread out during unoccupied periods. Thus, forwest facing windows the massive thermal storage could be reduced so thatthe heat is delivered more immediately.

The desired room illumination level is preferably determined by a timeof day/day of week clock combined with real time inputs of a manuallight switch or occupancy sensor. If the direct solar radiation is belowa threshold, the blind is preferably configured in Full View mode, andthe blinds are either set to a horizontal angle, or raised completely.If the direct solar radiation incident is above a threshold that wouldcause glare, the blind preferably goes into tracking mode. Firstpriority preferably is to achieve the desired illumination level. If theillumination setpoint is exceeded (as could occur if the room wasunoccupied and the setpoint is zero, or if the solar radiation isstrong), the controller preferably biases towards either heating orcooling. The selection of heating or cooling bias may be based on thestatus of the building HVAC system. It is proposed that the status ofthe building system be monitored from one or more central points of thebuilding energy control system, and the status broadcast wirelessly tothe blind controllers. This makes it unnecessary for the blindcontrollers to have knowledge of the room temperature or other details.

Furthermore, one of the desired features of a window is providing a viewto the outside for the building occupants. While the reflecting opticsdescribed herein do not allow unobstructed viewing at all times, thesystem described herein does have features to provide views. First, whendirect beam sunlight is not falling on the window, the blinds can be putat an angle that allows direct viewing between the louvers, or theblinds can be fully raised. When the louvers are in tracking mode, adirect view does exist between the louvers, depending on the angle ofthe sun and the focus point on the receiver. An alternative that canprovide a higher view fraction would be to cut microgrooves in thelouver and to form the effective mirror shape as a Fresnel techniquethat would have many narrow viewing slits in each mirror.

Having now fully set forth the preferred embodiments and certainmodifications of the concept underlying the present invention, variousother embodiments as well as certain variations and modifications of theembodiments herein shown and described will obviously occur to thoseskilled in the art upon becoming familiar with said underlying concept.It should be understood, therefore, that the invention may be practicedotherwise than as specifically set forth herein.

1. A window blind solar energy management system comprising: a firstlouver positioned adjacent a window; a second louver positioned adjacentsaid first louver, wherein said first louver is oriented with respect tosaid second louver to reflect light coming through said window towardsaid second louver; said second louver further comprising a solar energyredirection assembly oriented to receive reflected light from said firstlouver, said solar energy redirection assembly further comprising: alight reflection portion configured to reflect light from said firstlouver away from said window and into a room to which said window isattached; a heat absorption and radiation portion configured to absorbheat from reflected light from said first louver, and to radiate heatinto said room; and a light rejection portion configured to reflectlight from said first louver outward through said window.
 2. The windowblind solar energy management system of claim 1, wherein said firstlouver and said second louver are vertically suspended adjacent saidwindow and are pivotable so as to change an incidence angle of sunlightcoming through said window and striking said first and second louvers.3. The solar energy management system of claim 2, wherein said firstlouver and said second louver are vertically suspended from a housing,said housing further comprising at least one of a room temperaturesensor, an occupancy sensor, and an incoming solar radiation sensor. 4.The solar energy management system of claim 3, said housing furthercomprising motor controls operatively attached to said first louver andsaid second louver and configured to pivot said first louver and saidsecond louver.
 5. The solar energy management system of claim 4, whereinsaid motor controls are automatically responsive to a condition detectedby said at least one of a room temperature sensor, an occupancy sensor,and an incoming solar radiation sensor to pivot said first louver andsaid second louver.
 6. The solar energy management system of claim 1,said second louver further comprising a mirror adjacent said solarenergy redirection assembly, wherein said heat absorption and radiationportion is thermally insulated from said mirror.
 7. The solar energymanagement system of claim 6, wherein said heat absorption and radiationportion is attached to said mirror with a thermally insulating adhesive.8. The solar energy management system of claim 6, wherein said heatabsorption and radiation portion is attached to said mirror by aplurality of fins.
 9. The solar energy management system of claim 2,wherein said first louver and said second louver are pivotable toachieve a heating mode orientation in which sunlight passing throughsaid window reflects off of said first louver, and is directed into anarrow beam that impacts heat absorption and radiation portion on saidsecond louver, after which heat is radiated off of said heat absorptionand radiation portion towards a ceiling in said room.
 10. The solarenergy management system of claim 2, wherein said first louver and saidsecond louver are pivotable to achieve a lighting mode orientation inwhich sunlight passing through said window reflects off of said firstlouver, and is directed into a narrow beam that impacts said lightreflection portion on said second louver, after which light is reflectedoff of said light reflection portion towards a ceiling in said room. 11.The solar energy management system of claim 2, wherein said first louverand said second louver are pivotable to achieve a cooling modeorientation in which sunlight passing through said window reflects offof said first louver, and is directed into a narrow beam that impactssaid light rejection portion on said second louver, after which light isreflected off of said light rejection portion outward through saidwindow and away from said room.
 12. The solar energy management systemof claim 1, wherein said first louver further comprises a reflectivesheet having a concave upper surface.
 13. A window blind solar energymanagement system comprising: at least one pivotably mounted louver,said louver further comprising: a mirror; and a solar energy redirectionassembly positioned at a first end of said louver, said solar energyredirection assembly further comprising: a thermal receiver having asunlight receiving side having high absorbtivity and low emissivity, anda radiating side opposite said sunlight receiving side having highemissivity; an aperture positioned to allow light to pass through saidlouver; a secondary lighting mirror configured to reflect light passingthrough said aperture upward and away from said first end of saidlouver; and a secondary cooling mirror configured to reflect light awayfrom said louver.
 14. The solar energy management system of claim 13,wherein said mirror comprises a curved reflected surface configured toreflect incoming light into a narrow strip an adjacent surface.
 15. Thesolar energy management system of claim 14, wherein said adjacentsurface comprises a second pivotably mounted louver.
 16. The solarenergy management system of claim 13, wherein said secondary lightingmirror has a light diffusing surface comprising partially specular andpartially diffuse material.
 17. The solar energy management system ofclaim 13, further comprising a second pivotably mounted louver that isidentical in construction to said at least one pivotably mounted louver,wherein said louvers are vertically suspended adjacent a window and arepivotable so as to change an incidence angle of sunlight coming throughsaid window and striking said louvers.
 18. The solar energy managementsystem of claim 17, said system further comprising at least one of aroom temperature sensor, an occupancy sensor, and in incoming solarradiation sensor.
 19. The solar energy management system of claim 18,where said system is automatically responsive to a condition detected bysaid at least one of a room temperature sensor, an occupancy sensor, andan incoming solar radiation sensor to pivot said louvers.